Canon Pixma iP90 User Manual page 119

Borderless Printing (Print Dialog Box)
If you select Borderless Printing from the pop-up menu in the Print dialog
box, you can print the entire paper surface, so that no margins are left on the
four sides of the paper.
(1) Amount of Extension
When you select Borderless Printing, the sections that extend beyond
the paper are not printed because the image is enlarged to a paper size
slightly larger than the paper size. You can use a slide bar to adjust how
much the image extends beyond the paper. Usually, you need not to
adjust this setting. If you move the slide bar to the left to reduce the
extension amount, a border may appear.